A common valve assembly comprises a valve body and a valve member that moves relative to the valve body between a supply position and a nonsupply position. In one position, a sealing surface of the valve member seats against the sealing seat in the valve body. In the other position, the sealing surface is unseated from this sealing seat. To move the valve member from one position to the other, a “lifting force” is required to lift the valve member from the seat of this position, a “shifting force” is then required to shift the valve member to the other position, and a “sealing force” is then required to maintain a leakproof seating of the valve member. When a displacement device (e.g., an actuating device or a returning device) provides these forces, the lifting force and the initial shifting force are imposed early in the stroke, and the sealing force is imposed at the end of the stroke.